Dilatometric Study of Continuous Annealing of a Cold‐Rolled Austenitic Stainless Steel

Abstract

The sequence of structural changes produced in two deformed microstructures of austenitic stainless steel elaborated by a multipass unidirectional cold rolling (CR) and a two‐step one, to a 75% thickness reduction, is followed by dilatometric experiments. The two materials show different dilatometric behaviors. X‐ray diffraction and microhardness measurements are performed to underlie the observed dilatometric behaviors. The material subjected to multipass unidirectional CR shows an unusual dilatometric behavior. The first heating stage leads to the occurrence of the recovery reaction in competition with the ε‐martensite reversion. When the temperature increases between 550 and 780 °C, the reversion of deformation‐induced α‐martensite takes place and leads to a complicated dilatometric anomaly. Further increase in temperature leads to the occurrence of the recrystallization transformation. However, the material subjected to two‐step CR shows a quite usual dilatometric behavior which is explained by the occurrence of several reactions in the following order: 1) T < 300 °C, the recovery reaction, 2) 300 < T < 680 °C, the ferro‐ to paramagnetic transformation of α‐martensite, the reversion of ε‐martensite, and the athermal reversion of α‐martensite, 3) 680 < T < 760 °C, thermal reversion of DIM, and then 4) at T > 760 °C, the recrystallization.